Ubuntu 16.04 Low Graphics Mode

After a recent update (kernel?), I have begun to occasionally receive the message "Running in Low Graphics Mode" at boot (maybe half the time). I can tell it to use Default setting from the options it offers, and get by it, after which things look and work normally, even after some reboots.

I also usually get "System error detected, Report? at the same time, so I agree to report it.

I've seen some suggestion like :
# sudo apt-get update
# sudo apt-get remove ubuntu-desktop
# sudo apt-get install ubuntu-desktop
# sudo shutdown -r now
But these are all quite old, at least 3 years, up to 6 or more years, and some of the simple items in some of these (boot while holding (shift), ... just don't work, so I'm afraid of them.

I's unclear to me if this would wipe out my Gnome and Cinnamon, etc. installations, or if that is separate and safe. Please advise...